Aircraft transmission



5 sheets-sheet 1 R. CHILTON ErAL AIBCRAFT I TRANSMISSION Filed sept. 1o, 1958 Aug. 1s, 1942.

.D CHILTON WILLm/w 512522 f AT ORN E Aug. 18; 1942,. R. CHILTON Erm. s 293,279

AIRCRAFT TRANSMISSION Filed sept. 1'0, 193e ls sheets-sheet 2 www A ORNE ,tional arrangement'. l y Further, for the case of twin propellers andja Patented Aug. 18, 1942 Siesel, Verona, N. J., assignors to Wright Aeronautical Corporation, a corporation of New York Application september 10,1938, serial No. 229,286 (ci. 244-60) Claims.

This invention relates to gear and shaft transl mission systems in general, the specic embodiment of drawings being designed to drive propellers on the wings of an airplane from an engine mounted in the hull or fuselage. In conventional multi-propeller airplanes, the engines are mounted in nacelles on the wings with directly attached propellers, and such nacelles constitute elements of parasite drag and detract from the lift of the wing under high angle of attack conditions. Accordingly, it is often desired to submerge the ngines in the hull or fuselage. The

propeller tips must clear the sides of the fuselage lwhich involves relatively long transmission shafts where the engine is placed therein. l

The obvious layout consists 'of a bevel gear on the yengine power shaft, engaging a pinion which drives a lateral shaft engaging an outboard pinion meshed with a bevel gear on the propeller shaft, and the power is thus transmitted in series through two pairs of gears each transmitting the full load. Attempts to design such a. singlecontact bevel gear system result in driving gears of larger diameter than the engine crankcase andv requiring abnormally wide gears which are objectionable both as to weight and in the difculty ofy obtaining uniform contact throughout the great length of tooth involved. In the case of bevel gears,` tooth widths of more than a quarter of the radius of the gear are of` little avail since the pitch cone diameters at the inner end become too small. The present invention teaches the use of mutiple pinions and. shafts engaging common gears on the engine and propeller shaft respectively. This is achieved by either or both of two expedients: f

(a) Hypoid pinions are used having their cenand shafts;-

(b) The bevel gears are made double-facedk andpinions are engaged with both the front weight of the pinions and the bulk of the housings and also moderating the hypoicl offset dimension. In the case lllustrated,'the proportions are calculated for a 2000 H. P. engine, giving only 250 H. P. per pinion and shaft. The pinions and shafts run at four times engine speed in the instantcase so that the torque on each shaft becomes l/gX 1A=V32 of engine torque, whereby the shafts may be made of extremely small diameter as compared to the conventional case where the Atorque on the shaft is of the order of engine torque requiring large diameter tubular shafts.

Such r'igid shafts of the prior art introduce additional complication and weight in requiring universal joints to allow for wing deflection. According to the present invention, the diameter of the shaft is so insignificant compared to the depth of the wing spar that universal joints are intervals. The tube attachments to the engine ,and propeller gear housings are relatively rigid so that the deflections are confined to the midy portion of the tubes and shafts and therefore do not tend to misalign the ends of the shafts Irelative to the pinions which they engage.

' Other objects and advantages of the invention will be obvious from, or will be pointed out in the following description with reference to the drawings,inwhich: ,v l

Fig. lis a plan of a portion of an aircraft fus'elage'and wing showing the provisions of the inu vention in dotted lines;

Fig; 2 is a plan of the transmission organizai and back of the gears whereby a propeller may is reduced to one-quarter of that in the convensing'le central engine, this quadruple arrange-' are 4sub-divided over eight .tooth-contacts.

y menty may bev used at both sides o f the engine` gear and, accordingly,- the engine driving loads be, driven through four pinions and shafts in parallel whereby the load at each tooth contact A further feature ofv the invention follows Yfrom the'use of high speed .shafts whereby 'the pinion" I .diameters are.A relatively small, reducingfthe Fig. 3` is a section on the line 3--3 of Fig. 2; l

Fig. 4 is a' front elevation of thegear organization comprisingv a section on the line 4 4 of Fig. 2, and p Fig. 5 is afront elevation, shown partly in section and partlywth the front cover removed, ofl a part' ofthe transmission system.

.Referring first4 to Fig. 1, I0 designates an aircraft fuselage having va wing Il extending there- A from, the 'fuselage carrying a submerged power plantV l2 Ahaving a front gear housing I3. From :said housing aplurality of transmission 'shaft i housings extend laterally through the wing, terminatingin a.transmission unit Iii having a forsplines, 46 engaged by the splined wardly extending housing I6 through which passes a propeller shaft upon which a propeller I1 is mounted. The units I5 and I6 are provided with streamlined fairing indicated lat I8, and it will be noted that the cross-sectional area of the fairing I8 will be very small as compared with the frontal area of the'power plant I2. By the provisions of the invention, the large power plant I2 is wholly submerged within the fuselage in contradistinction to conventional practice in which engines are carried in wing nacelles, these nacelles having a substantial drag. By the elimination of the large wing nacelles and the substitution therefor of small fairings extending rearwardly from the propellers, a gain in aerodynamic cleaness in the airplane is afforded.

As above noted in the introductory remarks, a conventional bevel gear and shaft arrangement is unsatisfactory in an installation of this kind on account of the large parts which would be necessary and the high gear tooth loads which would be encountered. Reference may be now made to Figs. 2 to 5 inclusive which show the i-mproved transmission mechanism of the invention. 20 represents the power shaft of the power plant I2, upon which a double-faced spur toothed bevel gear 22 is mounted, the shaft 20 being piloted at its forward end in a bearing 23 carried by the housing I3. On each side of the housing I3, laterally extending rectilinearly disposed shafts 24, 25, 26 and 21 are journalled each of these shafts carrying at its inboard end a hypoid bevelpinion 29 engaged with one of the faces of the bevel gear 22. The bevel gear teeth are of the spur type, whereas the teeth of the pinions 29 are skewed to properly engage the gear teeth above and below the gear center. The outer ends of the shafts 24, 25, 26, and 21 drive pinions 30 engaged with a double-faced spur bevel gear 32 mounted on a propeller shaft 34, the latter being borne in and extending forwardly through the housing I6 to carry the propeller I1. The gears 30 and 32 are borne within the casing I5.

The several shafts 24, 25, 26, and 21 may be of quite small diameter since each, in an installation such as shown which has eight shafts, transmits one-eighth of the engine power. Due to the step-up gearing from the gear 22 to the pinions 29, the rotational speed of the shafts 24 to 21 is high and the torque is correspondingly lessened for the power transmitted. Thus, these shafts are light in weight and, may be quite exible obnoted that the bearing bores in the casing I5 and in the members 42 are symmetrical on each side of the casing center so that the pinions 30 may be alternately disposed on one or the other side of the center of thegear 32. Thus, casings I5 disposed on opposite sides of the power plant may be arranged as indicated in Fig. 2 for driving the outboard propellers of the aircraft in opposite directions by which propeller torque is cancelled out. For instance, in Fig. 4, assuming anti-clockwise rotation of the driving gear 22, the left-hand gear 32 is driven in a clockwise direction due to the engagement of the pinions 30 with the inboard side of the gear. 0n the right-hand side as shown, the high speed drive shafts extend to the outboard sides of the right-hand gear 32 by which anti-clockwise rotation of the right-hand gear 32 and its propeller is obtained. Again referring to Fig. 5, the pinions 30 may be disposed with equal facility on either the right or left-hand sides of the casing I5 and the high speed shafts 24 to 21 inclusive may be arranged to pass throughthe casing as shown in dot and dash lines. or may be arranged to pass into the casing for driving of the gear 32.

That side of the casing I5 from which the drive shaft and housings do not project may be closed by cover plates 50, while that side from which the shafts project receive the housing terminals 52 into which the housings 36 are telescoped.

In an installation of this character the thickness of the wing Il would approximate the diameter of the casing I5, and it will be seen that viating the necessity of universal joints therein and allowing for deflections of the wing II with respect to the fuselage I0 under flight loads. To

hold the shafts 24 to 21 from undue radial ex-` cursions, individual shaft housings 36 embrace each, and one or more steady bearings 38 may be provided between the shafts and housings to hold the latter elements in concentric relationship. The housings 36 may likewise be suiiiciently flexible to allow for load deection, but will be sufficiently stiff to hold their contained shatfs for true running. The shaft housings 36 are coupled to the casings I3 and I5 by telescoping joints as shown in Fig. 5 at 40, and may have intermediate supports as at 4l in Fig. 1.

In Fig. 5 the detailed construction of one of the casings I5 and its contained gearing is shown. Inboard bearing carriers 42 are provided and bearings '44 are carried by the casing itself, in which the pinions 30 are journalled, said pinions being hollow and being provided with internal end 48 of one or the other of the shafts 24 to 21. It will be any operating deflection to which wing spars may be subjected will induce insignificant bendingl stresses in the long slender tubes 36 and shafts 24 to 21. It will be understood that the propeller gear housings I5 are secured to wing structure and that, in view of the .flexibility of shafts and housings, this securement may be rigid.

The gear organization shown may be constructed as a propeller reduction gear as well as means for transmitting power from an engine to remote propellers, merely by selecting the proper ratios of gears in the housing I3 and in the housings I5. 'I'he power of a single engine is transmitted to two propellers through eight shafts and pinions, thereby reducing the tooth loads cn the propeller driving pinions to one-fourth of that in a conventional geared propeller drive. Further, if the pinions be organized for four times engine speed as shown, the torque on each, and on each extension shaft, will be one-thirty second of engine torque by which the shafts may be made very slender. ions 29 and 30, diagonally opposite pinions on one side of the gear will be identical so that, in the casing I3, there are but two different forms of pinions and similarly in each casing I5 there are but two different forms of pinions.

The showing indicates a two propeller drive from a single engine but it is apparent that the principles ofthe invention may be used for driving one propeller from a single engine or conversely, driving a greater number than two propellers from a single engine. The provisions of the invention likewise point to the possibility of coupling a plurality of propellers and engines together by light weight transmission means if such a coupling should be deemed desirable.

While we have described our invention in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding our invention, that various changes and modications may be made therein without departing It will be noted that, in the helical pin- Y from the spirit or scope thereof. We aim in the appended claims to cover all such modications and changes. y

We claim as our invention: i

1. In combination in aircraft comprising a central engine andpropellers spaced laterally therefrom, a pair of spaced propeller shafts having bevel gears, pinions respectively meshed with the inside run of,one of said gears and with the outside run of the other, a power bevel gear between said shafts and drivenby the engine, pinions engaged with respective sides of said gear, and a lateral shaft drivably connecting each power gear pinion with the respective propeller gear pinion.

2. In combination with an airplane having spaced apart propeller gear housingsin wings subject to relative deflection and an engine gear housing therebetween in a central body, lateral shafts between said body and wing housings, tubes surrounding said shafts, and rigid means connecting the ends of said tubes to respective housings against local deflection, said tubes and sufficiently exible intermediate said connections to yield to slight relative displacement of the respective housings and structures such as that incident to the deflection of the wings of the airplane in which the housings are installed.

4. In an aircraft comprising a body and wings, in combination, an input gear box in the body, a long, slender integral intermediate shaft extending therefrom through the wing, an output gear box in the Wing driven by said shaft, said boxes being subject to relative deiiection in service due' to wing loading, means on said boxes securing the respective ends of said shaft for alined shafts being flexible intermediate their ends tofl allow for deflection thereof upon deflection of the wings relative to the body.

3. In combination in aircraft, engine and propeller housings -each containing gears and mounted in relatively detlectable structures, lateral shafts connecting said gears, and lateral tubes housing said shafts and connecting said housings, the tube-to-housing connection being laterally rigid but the tubes and shafts 4being operation thereat,- and intermediate steady bearings along said shaft secured to the wing structure and` deectable with and with respect to said boxes.

5. In an aircraft comprising a body and wings, in combination, an input gear box in the body, a long, slender integral intermediate shaft extending therefrom through the wing, an output gear box 'in the wing driven by said shaft, said boxes being subject to relative deflection in service due towing loading, vmeans on said boxes securing the respective ends of said shaft for alined operation thereat, and a guide tube embracing said shaft and joining said boxes having steady bearings therealong secured to the wing structure and engaging said shaft; said tube being of sufficient resilience to allow of the relative deflection of said boxes.

ROLAND CHILTON. WILLIAM M. SIESEL. 

